Welcome to the Stobebolt
I'm not a big fan of driving on 60 year old brake lines, you only have one brake fluid circuit and if you blow a line your in for the ride of your life. Also, the parking brake is not meant to stop your truck when rolling down a hill at 50 mph...
More bad news...the rear rim shown in your picture is the Firestone RH-5 2-piece rim, they have been nicknamed the "widow maker" and were outlawed decades ago. If they are low on air DO NOT ADD AIR THEM UP, if you do they are a ticking time bomb...they can come apart at any time and for no reason, they rust around where the two halves lock together.
Be safe!
Mike B
